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IOO4                             Appendix V.

these limits, and j is a press button for trying if the float be
satisfactorily acting. At K the liquid rises through small holes to
L, and there is drawn by the suction through fine grooves on the
sides of an inverted cone, placed at the level of c, and the petrol
enters the chamber M as spray. Air is drawn inward at N, being
adjusted in quantity by the circular slide P actuated by lever R,
and constrained to pass into M in close contact with the spray.
The mixture passes through gauze into the higher chamber,
and is permitted to flow to the engine through inlet pipe Q,
being further regulated or throttled by the circular valve v,
actuated by lever u. A jacket x is supplied with hot exhaust
gas through the small pipe w, to perfect the gasification of the
P! '                           mixture.

Fig. 921 shews the arrangement of the carburettor and con-
nections, h being the petrol tank and / the starting or stopping
valve, g the flow-pipe to float chamber a, b the adjusting chamber
with levers/ to which passes the mixing air through pipe c from
near the hot engine cylinder d, / the exhaust from engine to ;//
the silencer, a portion of the products being abstracted, by way of
cock/, along pipe n to the warming jacket b of the carburettor,
and e is the inlet pipe to engine with inlet valve at k.

^ . ,•,                               jP. 768. Efficiency of Boilers.—The evaporation obtained

' **   ^                           in Ibs. of water per Ib. of coal, the former from and at 212°, is a

very ready way of comparing the thermal efficiency of boilers,
though giving no indication of other facts. The results following
may be taken as having been obtained with best Welsh coal of
about 14,500 thermal units calorific value per Ib. of fuel:—


Ordinary Lancashire boilers      ...        ...    ro  Ibs.

Galloway breeches boiler          ...        ...    r 2 "8 „

Babcock water-tube boiler        ......    12-6,,

Climax water-tube boiler          ...        ...    12 • 2 „

Thomycroft water-tube boiler    ...        ...    117,,

Belleville water-tube boiler       ...        ...    ri    „

Cochrane vertical boiler ...        ......      9 • i „